Gordon Brown signalled tonight that there would be no one-off payment to soften the impact of rising fuel bills in a package of measures expected to be released next week. But in a speech to the Scottish CBI, he sought to lift the gloom surrounding the wider economy, saying he was cautiously optimistic that underlying strengths would help Britain weather the global crisis.

Ministers had considered a direct payment to ease the impact of the rising fuel costs. But the package will instead centre on extra financial help from electricity producers to pay for home efficiency measures, targeted at low-income households. Brown is still hoping to tout the programme as worth £1bn, But Downing Street is concerned that the package will disappoint Labour backbenchers eager to see a big windfall tax on the electricity firms.

Brown said he was working up proposals with the utility companies. He told the Scottish CBI: "Not short-term gimmicks, or giveaways, but firm steps towards making every home in Britain more energy efficient, thus reducing bills not just temporarily, but permanently. You cannot address a long-term problem — the supply and demand for oil — with a short-term gimmick."

Government sources said all the additional direct government help to soften the impact of fuel bills had already been set out in the March budget when increases in the winter fuel allowance had been announced.

Ministers are instead focusing on extracting extra funding from the energy companies for the carbon emissions reduction target programme, a £1.5bn, three-year obligation on energy suppliers to install home-based energy efficiency measures for people on low incomes, those with disabilities and those aged over 70. But talks with the energy firms are incomplete.

Richard Lambert, the CBI director general, warned against a windfall tax, saying the worst way to assist the fuel-poor "would be to impose an arbitrary and unfair tax on the energy industry, just at a moment when we want those same companies to be preparing for vastly increased investment in our energy infrastructure". But the Local Government Association claimed the big six electricity producers had boosted dividend payments to shareholders by £257m over the last year, suggesting they were not ploughing their profits into investment.

Brown said he was "cautiously optimistic about the long-term resilience and underlying strengths of the British economy." He said: "At root our economy is better placed to weather any global economic storm than it was the 70s, 80s or early 90s".

After chancellor Alistair Darling's more gloomy forecasts in his recent Guardian interview, Brown said he rested his cautious optimism on continued historically low interest rates, subdued wage pressures, fast-growing productivity, continued low levels of public debt as a proportion of national income, and the "most robust independent competition regime anywhere in the world". The government would not let down hard-working families on modest and middle income families: "We will ensure that no one who is prepared to work hard and adapt to change will lose out as a result of global forces."

But Britain could not pull up the drawbridge, or be immunised against the first great financial crisis of the global age, a crisis allied to a "global credit crunch and global rises in commodity prices".

The shadow chancellor, George Osborne, said: "The prime minister is in denial about both the crisis of confidence in his leadership and the economic crisis facing the country. His speech is totally at odds with the bleak assessment given by his chancellor just five days ago.

"At a time when Britain needs strong and united leadership with a clear sense of direction, we have a Labour government descending into civil war and a chancellor and a prime minister who publicly disagree on the severity of the problems we face."